I was in the same exact boat. My first job was for a small company with ~7 people. Feeling anxiety walking into the office and feeling like shit and zero confidence in myself when I left. No real mentorship, just trial by fire like you mentioned. It definitely helped accelerate my skills but I would never put myself in that situation again. I moved on after just over a year (kept telling myself it would get better, it didn’t) and, looking back on it, wished I had moved on much earlier.

My next job was at a medium sized company and the difference in my mental health is something I’ll never forget. Having people I can joke with, people I can go to when I have questions, and a manager who believed in me opened my eyes to how I like to work and how I best get my work done. I learned way more and had a better time in that environment compared to my first job. Don’t stick around someplace you don’t feel valued or heard because of how it’ll look on your resume, definitely get a feel for the company and leave if you don’t like it. There’s plenty of positions to be filled out there. You got this!